雨季白洋淀地区散养鸭粪中氮素去向研究

Environmental fate of released nitrogen from scatteredfeeding duckfeces during rainy seasons in the Baiyangdian Lake Region

散养是白洋淀地区养鸭的主要方式,散养过程中产生的大量鸭粪因不够集中、难以收集而残留于土壤表面。借助小区模拟试验,研究了白洋淀雨季(6～9月份)残留在土壤表面的鸭粪中氮素动态变化及环境影响因素。结果表明:鸭粪中部分氮素以NH3的形式挥发,挥发期为45d左右,挥发量约为8.72kg·hm-2;NH3挥发主要集中在鸭粪排出后的7d内,挥发初期随温度降低、湿度增加和光照减弱逐渐降低,随着挥发的减弱其与环境因素相关性不明显。模拟小区地表径流中总氮(TN)流失负荷为10.05kg·hm-2,以颗粒态氮(PN)为主;可溶态氮(TDN)中,以无机氮为主。淋溶水中总氮淋失负荷为19.30kg·hm-2,以NO3--N为主。自然状态下,鸭粪中约10%氮素以NH3挥发、地表径流和淋溶流失;部分氮素残留于土壤中,另有部分未矿化鸭粪存在于土壤表面,约占鸭粪总量的45.09%。残留于土壤中的氮素一旦达到土壤临界值,将威胁当地水环境安全,因此必须采取有效措施,防止养鸭带来的过量氮素累积造成的环境污染。

Scatteredfeeding is an important duck breeding mode in the Baiyangdian Lake Rgion （BLR）. During breeding, it is always hard to collect duckfeces because of the lack of concentrated breeding. Hence most duckfeces are abandoned on the soil surface. This paper stimulates a plot experiment condition to study the dynamics of released nitrogen from scattered feeding duckfeces and how they are influenced by environmental factors in BLR in rainy season of June to September. Investigation shows that during the reason part of nitrogen in duckfeces losses as NH3 and NH3 volatilization lasting for about 45 days at 8.72 kg·hm2. The first 7 days are critical for NH3 volatilization, accounting for 82.7% of the total content. Volatile flux decreases gradually with decreasing temperature, illumination and increasing humidity and becomes insignificantly correlated with the environment factors. The load of total nitrogen loss in runoff is 10.05 kg·hm2, with the highest proportion of particle nitrogen in the duckfeces treatment. There is increasing concentration of inorganic nitrogen in dissolved total nitrogen. Total nitrogen loss in leached water is 19.30 kg·hm2 in duckfeces treatment, with the highest proportion of nitrate nitrogen. Under natural conditions, nitrogen loss through leaching, volatilization and runoff accounts for about 10% of total nitrogen in duckfeces. Nonmineralized nitrogen in duckfeces on soil surface plus nitrogen remaining in soil accounts for 45.09%. Once soil nitrogen content exceeds the critical value, it threatens water safety in BLR. Hence it is so urgent to adopt effective countermeasures that would eliminate hidden risks in freerange poultry in BLR.